在 ViewPager2 中使用 Pager 适配器

问题描述

我正在尝试创建一个欢迎滑块，但在调用 slideView.setAdapter(sliderAdapter); 时出现问题。有一个错误说

必需的类型适配器，提供 SliderAdapter

我使用的是 ViewPager2 并且我使用的是旧的 ViewPager 适配器。有问题吗？

package com.example.leblood;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.constraintlayout.widget.ConstraintLayout;
import androidx.viewpager.widget.PagerAdapter;

public class SliderAdapter extends PagerAdapter {

Context context;
LayoutInflater layoutInflater;

public SliderAdapter(Context context){
    this.context = context;
}

public int[] slide_images = {

        R.drawable.donat,R.drawable.request,R.drawable.bloodmap

};

public String[] slide_heading = {

  "Donate Blood","Request Blood","Track Requests"

};

public String[] slide_desc = {

        "You can donate at any time just by filling the form","Request any type of blood anywhere in Lebanon","Track blood requests,donation centers and pinpoint their location"

};


@Override
public int getCount() {
    return slide_heading.length;
}

@Override
public boolean isViewFromObject(View view,Object object) {
    return view == object;
}


@NonNull
@Override
public Object instantiateItem(ViewGroup container,int position) {
    layoutInflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE);
    View view = layoutInflater.inflate(R.layout.slider,container,false);

    ImageView slideImageView = (ImageView) view.findViewById(R.id.slide_image);
    TextView slideheading = (TextView) view.findViewById(R.id.slide_heading);
    TextView slideDescription = (TextView) view.findViewById(R.id.slide_desc);

    slideImageView.setimageResource(slide_images[position]);
    slideheading.setText(slide_heading[position]);
    slideDescription.setText(slide_desc[position]);

    container.addView(view);
    return view;
}

@Override
public void destroyItem( ViewGroup container,int position,Object object) {
    container.removeView((ConstraintLayout)object);
}
}

package com.example.leblood;

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;

import android.os.Bundle;
import android.widget.LinearLayout;

public class MainActivity extends AppCompatActivity {

    private ViewPager2 slideView;
    private LinearLayout dots;
    private SliderAdapter sliderAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        slideView = findViewById(R.id.SlideviewPager);
        dots = (LinearLayout) findViewById(R.id.dots);

        sliderAdapter = new SliderAdapter(MainActivity.this);
        slideView.setAdapter(**sliderAdapter**);
    }
}

<LinearLayout
    android:id="@+id/dots"
    android:layout_width="80dp"
    android:layout_height="77dp"
    android:layout_marginTop="6dp"
    android:orientation="horizontal"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/SlideviewPager">

</LinearLayout>

<androidx.viewpager2.widget.ViewPager2
    android:id="@+id/SlideviewPager"
    android:layout_width="match_parent"
    android:layout_height="779dp"
    tools:ignore="MissingConstraints">

</androidx.viewpager2.widget.ViewPager2>

</androidx.constraintlayout.widget.ConstraintLayout>

解决方法

ViewPager2 使用 RecyclerView.Adapter 提供其内容。因此，您可以将旧的 ViewPager 与当前的适配器一起使用（我不建议这样做），也可以迁移到新的适配器。

它们实际上提供了全面的 migration guide，因此我建议您查看一下，特别是如果您以前从未使用过 RecyclerView。